The impacts of a strengthening Pacific El Niño climate pattern are beginning to impact Northland, according to Northland Regional Council.
By Susan Botting, Local Democracy Reporter
"Impacts on Northland's weather patterns are starting to be felt and will persist through this outlook period," Northland Regional Council (NRC)'s August climate and hydrology report said.
El Niño conditions strengthened considerably during August and have shown the strongest warming trend on record,with impacts on Northland's weather patterns already beginning to emerge, the report said.
NRC's chief executive Jonathan Gibbard told the council's mid-September Te Ruarangi committee meeting this El Niño climate pattern could quite possibly be the strongest on record and bring conditions unlike anything previously experienced in Northland.
The report said peak El Niño conditions were expected in late spring or early summer.
The developing El Niño was comparable to the powerful 1997-98 climate pattern – one of the strongest El Niño events ever recorded globally, it said.
This brought drought conditions to parts of New Zealand and significant impacts on farming and water resources.
El Niños typically brings more frequent westerly winds and drier conditions to Northland, increasing the likelihood of below-average rainfall, lower river flows and reduced groundwater recharge.
Forecasters say below-average rainfall is now the most likely outcome for the September to November period, while temperatures were more likely to be above average.
The report says that outlook comes despite Northland recording 172mm of rain in August, 108% of the long-term average for the month.
The ocean has flipped from La Niña to a fast-intensifying El Niño in a matter of months, with more profound impacts expected for New Zealand. (Source: Supplied)
Most of that rain arrived in late August when a burst of subtropical weather lifted totals across the Far North, Hokianga and eastern coastal areas from the Bay of Islands to Whangārei Heads.
The late burst of rain provided welcome relief, but the report said it has not erased concerns about a strengthening El Niño.
The rain came after significantly drier conditions during July.
Meanwhile, Northland's August river flows ranged from "normal" to "extremely low". The rivers were predominantly classified as "below normal" to "very low", particularly across western, mid-north and southern parts of the region.
August's rain improved river flows along parts of Northland's east coast from the Bay of Islands to Whangārei Heads, but waterways through its western, mid-north and southern areas remained generally below normal.
Groundwater levels had improved following the late August rain, with the additional rainfall helping recharge many aquifers.
Most monitored groundwater sites remain either normal or below normal for this time of year.
Chief Scientist of Weather and Climate Forecasting at Earth Sciences New Zealand, Chris Brandolino speaks to Breakfast about the weather pattern. (Source: Breakfast)
But groundwater levels were classed as extremely low at Taipā and Awaroa near Kaitaia in the Far North and low at Poroti and Maungatapere west of Whangārei, and Maunu on Whangārei's urban fringe.
Northland's winter rainfall was 82% of the seasonal average, despite August's burst of rain.
The highest rainfall was at Touwai near Whangaroa Harbour where 325.5mm or 147% of normal August rainfall was recorded.
The lowest rainfall was at Dargaville where 60.2mm or 48% of its normal August rain was recorded.
Cape Reinga received 186.9mm or 181% of its normal August rainfall, while Marsden Point recorded 178mm or 148%.
In contrast Kaikohe, Opouteke west of Whangārei, areas south of Whangārei towards the Northland/Auckland boundary and parts of Kaipara between Kai Iwi Lakes and Poutō Point all recorded below average rainfall.
Soil moisture had received a significant boost from August rain and was at or near field capacity across most of the region as a result.
This gives the region more moisture in reserve as it heads into spring and a cushion should the weather turn dry.
However, the report suggests that cushion may prove difficult to maintain, with Northland's spring rainfall most likely to be below average.
The districts at a glance
Far North district was the biggest beneficiary of August's rainfall, with heavy falls across parts of the Bay of Islands, Hokianga and Mid North pushing many areas above normal for the month.
However, groundwater concerns remained with extremely low levels still recorded at Taipā and Awaroa near Kaitaia, while Kaikohe was among the areas that remained drier than average.
Whangārei district experienced a mixed month. Eastern coastal areas and communities such as Whakapara and Punaruku were among Northland's wetter locations, but western catchments and some groundwater sites remained below normal, while river flows continued to lag despite the rainfall.
El Niño is expected to bring a warm, dry and windy spring – putting pressure on crops, pasture, and water supplies. (Source: Breakfast)
Kaipara district was generally the driest of Northland's three districts, with below-average rainfall recorded across areas between Kai Iwi Lakes and Pouto Point.
Dargaville recorded the region's lowest monthly rainfall total, highlighting the district's relatively dry conditions despite Northland's above-average rainfall overall.
– Local Democracy Reporting is local body journalism co-funded by RNZ and NZ On Air
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